Film-type semiconductor conductive modules which have conventionally been utilized as solar cells, photosensors, etc. have a thin-film construction in which units each having a number of photovoltaic regions connected in series are arranged on the same plane in order that the modules capture as much light as possible in limited spaces and convert the light into electric energy.
FIG. 3 is a plan view illustrating the construction of a conventional amorphous silicon (hereinafter referred to as a-Si) solar cell in which solar cell unit elements are connected in series on an insulating substrate plate, each solar cell unit element comprising a transparent electrode layer, an a-Si layer as an amorphous semiconductor layer, and a conductive printed electrode layer as a back electrode layer, superposed in this order. As illustrated, this a-Si solar cell comprises a single glass substrate plate 1 and, superposed thereon, a transparent electrode layer 2 (21-23), an a-Si layer 3 (31-33), and a conductive printed electrode layer 4 (41-43), thus forming a plurality of solar cell unit elements. These solar cell unit elements are connected in series by bringing the conductive printed electrode layer in an element into contact with the transparent electrode layer of an adjacent element.
In manufacturing this kind of solar cell, a transparent conductive film, such as an ITO (indium tin oxide) or SnO.sub.2 (tin oxide) film or the like, is first formed over a glass substrate plate 1 at a thickness of about 500 to 10,000 .ANG. by electron beam vapor deposition, sputtering, or the thermal CVD process. A transparent electrode layer 2 is then formed by patterning the transparent conductive film by means of a laser beam, or by forming a patterned photoresist on the transparent conductive film by photolithography and subjecting the resulting transparent conductive film to etching.
An a-Si layer 3 is then formed, for example, by depositing on the transparent electrode layer 2 a p-type a-Si layer at a thickness of about 200 .ANG., an undoped a-Si layer at 0.2-1 .mu.m, and an n-type a-Si layer at about 500 .ANG., by the plasma discharge decomposition of silane gases. The p-type a-Si is obtained by doping boron and carbon, while the n-type a-Si is obtained by doping phosphorus. The thus-formed a-Si layer 3 is patterned, or divided, into regions 31, 32, and 33 by means of a laser beam. Subsequently, a patterned conductive back electrode layer 4 is formed by printing to prepare a solar cell.
If, in the above process, a YAG laser beam used to pattern the transparent conductive film and having a wavelength of 1.06 .mu.m is used for the patterning of the a-Si layer, the power of the laser beam should be heightened because of the low absorbance of the a-Si layer, and patterning of the a-Si layer with such a higher-power laser beam damages the transparent electrode layer at the regions 26 and 27 shown in FIG. 3 which are exposed to the laser beam. In order to avoid such a problem, a YAG laser beam with a wavelength of 0.53 .mu.m, which is well absorbed by a-Si layers, has conventionally been used for the patterning of a-Si layers. Therefore, conventional patterning has been disadvantageous in that the laser necessarily has a complicated structure because it should be so constructed as to emit laser beams with different wavelengths respectively suited for transparent conductive films and a-Si layers, and that good reproducibility is not obtained because reflectance varies depending on the state of a-Si layer surfaces.